#coding:utf-8
class ListContainer:
    _data = []
    _maxlen = 0
    _readcnt = 0
    def __init__(self, Data = []):
        self._data = Data
        self._maxlen = len(Data)
    def next(self):
        if self._readcnt < self._maxlen:
            l = self._data[self._readcnt]
            self._readcnt += 1
            return l
        else:
            return None
    
    def goto_first(self):
        self. _readcnt = 0